Special exception for EMFILE / ENFILE when using sockets.

[Norman Maurer]

If we go this route we should also reconsider:

https://bugs.openjdk.java.net/browse/JDK-8167161 <https://bugs.openjdk.java.net/browse/JDK-8167161>

Still not sure what solution I would prefer tho.


> On 6 Dec 2016, at 12:14, Langer, Christoph <christoph.langer at sap.com> wrote:
> 
> Hi,
>  
> I would also support if IOException could be enriched to expose the native error code. However, the user then would need to evaluate this code in a platform specific manner. Maybe there could be some class/interface which would help to translate platform specific error codes to common constants for common error types.
>  
> Best regards
> Christoph
>   <>
> From: net-dev [mailto:net-dev-bounces at openjdk.java.net] On Behalf Of Bernd Eckenfels
> Sent: Montag, 5. Dezember 2016 20:09
> To: net-dev at openjdk.java.net
> Subject: Re: Special exception for EMFILE / ENFILE when using sockets.
>  
> Hello,
>  
> I know it is a radical idea, but what about exposing errno value in an IOException.
>  
>  I do think that the new ConnectionRefused subtype is helpful, but for each seldomly occuring error case a dedicated exception is more work than a one time mapping of native errormcodes to fields.
> 
> Gruss
> Bernd
> -- 
> http://bernd.eckenfels.net <http://bernd.eckenfels.net/>
>  
> 
> 
> 
> On Mon, Dec 5, 2016 at 7:28 PM +0100, "Norman Maurer" <norman.maurer at googlemail.com <mailto:norman.maurer at googlemail.com>> wrote:
> 
>  
>  
> > Am 05.12.2016 um 18:48 schrieb David M. Lloyd :
> > 
> >> On 12/05/2016 06:29 AM, Norman Maurer wrote:
> >> Hi all,
> >> 
> >> I wonder if it would be possible to add a new public exception time for the situation of an SocketChannel.accept(…) or SocketChannel.open(…)  (and the same for ServerSocket / Socket) failing because of too many open files.
> >> The reason is because especially when acting as a server such an exception may be something you can easily recover from. At there is basically no way to detect if this was the cause of an IOException or not.
> >> 
> >> On unix / linux this are the errno values:
> >> 
> >> [EMFILE]           The per-process descriptor table is full.
> >> [ENFILE]           The system file table is full.
> >> 
> >> For netty we would love to be able to know if this was the case of the problem and if so just stop accepting for a period of time to help the system to recover.
> >> 
> >> What others think about this ?
> > 
> > I like the idea, but maybe it should be a general IOException since this same error can happen on file open, selector creation (sometimes), pipe creation, etc.
> > 
> > -- 
> > - DML
>  
> Sure that would work for me as well :)
>  
> Bye,
> Norman

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